Ethics as a subject begins with the works of Aristotle. In its original form, this subject is concerned with the question of virtue (Greek aretē) of character, the acquisition of which is in turn aimed at living well and eudaimonia, a Greek word often translated as well-being or happiness. In other words, ethics is a systematic study of how individuals should best live. This study was originally coupled with the closely related study of politics, especially law making which has an effect on how people are brought up, which looked at the same question from the standpoint of the community. The original Aristotelian and Socratic answer to the question of how best to live was to live the life of philosophy and contemplation.

Three ethical treatises

All three may have been compiled by students of Aristotle, especially the Magna Moralia, but they are all considered to be quite similar in the material covered and the method of covering it. (The Magna Moralia is sometimes considered to be a more summarized format.) The Nicomachean Ethics has received the most scholarly attention, and is the most easily available to the public in many different translations and editions. Some critics consider the Eudemian Ethics to be "less mature," while others, such as Kenny (1978), contend that the Eudemian Ethics is the more mature, and therefore later, work. Books IV-VI of Eudemian Ethics also appear as Books V-VII of Nicomachean Ethics.

Traditionally it was believed that the Nicomachean Ethics and the Eudemian Ethics were either edited by or dedicated to Aristotle's son and pupil Nicomachus and his disciple Eudemus, respectively, although the works themselves do not explain the source of their names. Although Aristotle's father was also called Nicomachus, Aristotle's son was the next leader of Aristotle's school, the Lyceum, and in ancient times he was already associated with this work.

A fourth treatise, Aristotle's Politics, is often regarded as the sequel to the Ethics; Aristotle's Ethics states that the good of the individual is subordinate to the good of the city-state, or polis.

Aristotle as a Socratic

Aristotle's ethics builds upon earlier Greek thought, particularly that of Aristotle's teacher Plato and Plato's teacher, Socrates. One important distinction is that Socrates didn't leave any written work, and Plato left only some letters and works written as dialogues (in which Plato himself is never a major character). It is therefore the works of Aristotle which appear at first sight to be easiest to use. The overall direction of each of these philosophers, however, was quite similar, and all three (along with Xenophon) are generally referred to as "Socratic".

According to Aristotle in his Metaphysics, Socrates was the first Greek philosopher to concentrate on ethics, although he apparently did not give it this name, as a philosophical enquiry concerning how people should best live. Aristotle dealt with this same question but giving it two names, "the political" (or Politics) and "the ethical" (Ethics), both with Politics being the name for the two together as the more important part. The original Socratic questioning on ethics started at least partly as a response to sophism, which was a popular style of education and speech at the time. Sophism emphasized rhetoric, and argument, and therefore often involved criticism of traditional Greek religion and flirtation with moral relativism.

Aristotle's ethics, or study of character, is built around the premise that people should achieve an excellent character (a virtuous character, "ethikē aretē" in Greek) as a pre-condition for attaining happiness or well-being (eudaimonia). It is sometimes referred to in comparison to later ethical theories as a "character based ethics". Like Plato and Socrates he emphasized the importance of reason for human happiness, and that there were logical and natural reasons for humans to behave virtuously, and try to become virtuous.

Aristotle's treatment of the subject is distinct in several ways from that found in Plato's Socratic dialogues.

Aristotle's presentation is obviously different from Plato's because he does not write in dialogues, but in treatises. Apart from this difference, Aristotle explicitly stated that his presentation was different from Plato's because he started from whatever could be agreed upon by well brought-up gentlemen, and not from any attempt to develop a general theory of what makes anything good. He explained that it was necessary not to aim at too much accuracy at the starting point of any discussion to do with controversial matters such as those concerning what is just or what is beautiful. (From this starting point however, he built up to similar theoretical conclusions concerning the importance of intellectual virtue and a contemplative life.)

Rather than discussing only four "cardinal virtues" of Plato (courage, temperance, justice, and prudence), all three of the ethical works, starts with courage and temperance as the two typical moral virtues which can be described as a mean, then discusses a whole range of minor virtues and vices which can be described as a mean, and only then discusses justice and the intellectual virtues. Aristotle places prudence (phronēsis, often translated as practical wisdom) amongst these intellectual virtues. (Nevertheless, like Plato he eventually says that all the highest forms of the moral virtues require each other, and all require intellectual virtue, and in effect that the happiest and most virtuous life is that of a philosopher.)

Aristotle emphasizes throughout all his analyses of virtues that they aim at what is beautiful (kalos), effectively equating the good, at least for humans, with the beautiful (to kalon).

Aristotle's analysis of ethics makes use of his metaphysical theory of potentiality and actuality. He defines happiness in terms of this theory as an actuality (energeia); the virtues which allow happiness (and enjoyment of the best and most constant pleasures) are dynamic-but-stable dispositions (hexeis) which are developed through habituation; and this pleasure in turn is another actuality that compliments the actuality of happy living.

Practical ethics

Aristotle believed that ethical knowledge is not only a theoretical knowledge, but rather that a person must have "experience of the actions in life" and have been "brought up in fine habits" to become good (NE 1095a3 and b5). For a person to become virtuous, he can't simply study what virtue is, but must actually do virtuous things.

We are not studying in order to know what virtue is, but to become good, for otherwise there would be no profit in it. (NE 2.2)}}

Aristotle's starting point

As mentioned above, the Aristotelian Ethics all explicitly aim to begin with approximate but uncontroversial starting points. Aristotle's starting point is that everything humans do is aimed at some good, with some good higher than others. The highest human good which people aim at is, he said, is generally referred to as happiness (Gk. eudaimonia - sometimes translated as "living well").

Aristotle asserted that popular accounts about what life would be happy divide into three most common types: a life dedicated to vulgar pleasure; a life dedicated to fame and honor; or a life dedicated to contemplation. To judge these, Aristotle uses his method of trying to define the natural function of a human in action. A human's function must include the ability to use reason or logos, because this is an essential attribute of being human. A person that does this is the happiest because he is fulfilling his purpose or nature as found in the rational soul.

The question of how to be happy therefore becomes a question of which activities of the human soul represent the highest excellence in using reason.

Aristotle proposed that we could accept it when people say that the soul can be divided into three parts: the Nutritive Soul (plants, animals and humans), the Perceptive Soul (animals and humans) and the Rational Soul (humans only).

Moral virtue

Moral virtue, or excellence of character, concerns what we do voluntarily, and not what we do because we are forced to do so. The traditional word for the opposite of virtue is vice.

Aristotle believed that every ethical virtue or positive character trait can be described as a pleasant intermediate activity, between a painful excess and a painful deficiency. But seeing what is most pleasant and most painful in truth is not something everyone can easily do, especially if they are badly brought up and not experienced. Another way Aristotle describes each of the moral virtues is as a correct aiming at what is beautiful (kalos).

For example, courageous (or literally manly) action is a mean between the painful activities of fear and rash overconfidence. Too much fear or too little confidence leads to cowardice, and too little fear or too much confidence can lead to rash, foolish choices. (Such philosophies of aiming at a middle ground are often referred to as The Golden Mean.) But courage is also described as an ability to rationally choose the beautiful, which in some cases can be a beautiful death.

Aristotle distinguishes virtue and vice in their true sense as stable dispositions (hexeis) about what they would consciously choose between perceived pleasant and painful options. Dispositions to feel emotions are distinguished by Aristotle as something other than virtues or vices, although they can also be seen as a mean between two extremes, and these are also to some extent a result of up-bringing and habituation. Two examples of such dispositions would be modesty, or a tendency to feel shame, which Aristotle discusses in NE IV.9; and righteous indignation (nemesis), which is a balanced feeling of sympathetic pain concerning the undeserved pleasures and pains of others. Exactly which habitual dispositions are virtues or vices and which only concern emotions, differs between the different works which have survived, but the basic examples are consistent, as is the basis for distinguishing them in principle.

Some people, despite their perceptions and habits concerning what they think is beautiful and pleasant, act on the basis of emotions, even though it is not what they choose. This is not vice according to Aristotle's definition, but "akrasia", sometimes called weakness of will or lack of self-mastery in English translations. In English, the person who would choose the virtuous option but does not, is sometimes translated as "incontinent" in opposition to having vice or being "vicious".

One apparent emotion is separated from the others and not treated as an emotion by Aristotle, and this is "thumos", the spiritedness which is the cause of anger. Aristotle, like Plato in his Socratic dialogues, treats thumos as an important and positive part of the human soul, which helps a well brought-up young person become virtuous. Thumos is not an emotion (pathos) according to Aristotle because it tries to follow the leadership of the rational part of the soul which makes conscious decisions. The true emotions on the other hand, are able to distort rational thinking and dominate it.

Aristotle's described how people become virtuous by performing virtuous actions, which they might not have chosen themselves when young. They must develop proper habits during childhood and this usually requires help from teachers, parents, and law-makers. A good community is normally required for the development of good people.

Virtue in the highest sense, in an adult who has been brought up well, will not just involve good personal habits such as courage and temperance, but also friendship and justice and intellectual virtue.

Justice

Aristotle also wrote about his thoughts on the concept of justice in the Nicomachean Ethics. In these chapters, Aristotle defined justice in two parts, general justice and particular justice. General justice is Aristotle’s form of universal justice that can only exist in a perfect society. Particular justice is where punishment is given out for a particular crime or act of injustice. This is where Aristotle says an educated judge is needed to apply just decisions regarding any particular case. This is where we get the concept of the scales of justice, the blindfolded judge symbolizing blind justice, balancing the scales, weighing all the evidence and deliberating each particular case individually. Homonymy is an important theme in Aristotle’s justice because one form of justice can apply to one, while another would be best suited for a different person/case.
Aristotle says that developing good habits can make a good human being and that practicing the use of The Golden Mean when applicable to virtues will allow a human being to live a healthy, happy life.

The highest good

In his ethical works, Aristotle describes several apparently different kinds of virtuous person as necessarily having all the moral virtues, excellences of character.

Being of "great soul" (magnanimity), the virtue where someone would be truly deserving of the highest praise and have a correct attitude towards the honor this may involve. This is the first such case mentioned in the Nicomachean Ethics.

Being just in the true sense. This is the type of justice or fairness of a good ruler in a good community.

Aristotle also says, for example in NE Book VI, that such a complete virtue requires intellectual virtue, not only practical virtue, but also theoretical wisdom. Such a virtuous person, if they can come into being, will choose the most pleasant and happy life of all, which is the philosophical life of contemplation and speculation.

Aristotle claims that a human's highest functioning must include reasoning, being good at what sets humans apart from everything else. Or, as Aristotle explains it, "The function of man is activity of soul in accordance with reason, or at least not without reason." He identifies two different ways in which the soul can engage: reasoning (both practical and theoretical) and following reasoning. A person that does this is the happiest because they are fulfilling their purpose or nature as found in the rational soul.

(The wise person will) be more than human. A man will not live like that by virtue of his humanness, but by virtue of some divine thing within him. His activity is as superior to the activity of the other virtues as this divine thing is to his composite character. Now if mind is divine in comparison with man, the life of the mind is divine in comparison with mere human life. We should not follow popular advice and, being human, have only mortal thoughts, but should become immortal and do everything toward living the best in us. (NE 10.7)

In other words, the thinker is not only the 'best' person, but is also most like God.

Influence on later thinkers

Aristotle's writings were taught in the Academy in Athens until 529 AD when the Byzantine EmperorJustinian I closed down non-Christian schools of philosophy.

Aristotle's work however continued to be taught as a part of secular education. Aristotle's teachings spread through the Mediterranean and the Middle East, where some early Islamic regimes allowed rational philosophical descriptions of the natural world. Alfarabi was a major influence in all medieval philosophy and wrote many works which included attempts to reconcile the ethical and political writings of Plato and Aristotle. Later Avicenna, and later still Averroes, were Islamic philosophers who commented on Aristotle as well as writing their own philosophy in Arabic. Averroes, a European muslim, was particularly influential in turn upon European Christian philosophers, theologians and political thinkers. Jewish philosophers such Maimonidies helped to develop these thoughts and also to transmit them around the Mediterranean.

In the twelfth century, Latin translations of Aristotle's works were made, enabling the Dominican priest Albert the Great and his pupil Thomas Aquinas to combine Aristotle's philosophy with Christian theology. Later medieval church scholasticism in Western Europe insisted on Thomist views and suppressed non-Aristotelian metaphysics. Aquinas wrote detailed commentaries of Aristotle, including his Nicomachean Ethics, and his most well-known work, the Summa Theologiae contained fifteen volumes which were concerned with ethics. It argued that a rational foundation for ethics was compatible with Christianity, enabling it to borrow many ideas from the Nicomachean Ethics. Eudaimonia or human flourishing was held to be a temporary goal for this life, but perfect happiness as the ultimate goal could only be attained in the next life by the virtuous. New theological virtues were added to the system: faith, hope and charity. Supernatural assistance was also allowed, helping people to be virtuous. Many important parts of Aristotle's ethics were retained however. Thomism, the name given to the beliefs of Thomas Aquinas, is particularly influential: it has been a part of official Catholic doctrine since the time of Pope Leo XIII (1878–1903).

In the early 16th century, Niccolò Machiavelli, while heavily influenced by writers who had been in turn influenced by Plato and Aristotle, such as PolybiusPlutarch, argued for a realism in political and ethical thinking which was not compatible with the Socratic approach of taking bearings from non-existent ideal cities and ideal types of human behaviour. This criticism spread to the physical sciences. The empiricism of early modern science challenged Aristotle's physics and metaphysics so successfully that doubt was cast on the rest of his philosophy too. The Nicomachean Ethics nevertheless continues to be treated as a relevant work for philosophers today however. Although Aristotle's ethics was integrated with an Aristotelian metaphysical understanding of reality which is no longer commonly accepted in science, it is not universally accepted that this makes his ethics wrong.